This invention relates to an adjustable boring head tool holder and has specific relevance to the attachment of a boring bar to a boring bar holder for an initial rough cut and subsequent finer finishing cuts.
Heretofore, boring head tool holders include a boring bar which carries at one end the cutting tool for cutting a bore in a workpiece. The other end of the bar is attached to a bar holder. The bar includes an eccentric shank which fits into an eccentric bore in the bar holder. The holder is adapted for securement within the spindle of a boring mill. The bar is aligned with the rotational axis of the holder during an initial rough cut and is then rotated relative to the holder to offset the axis of the bar from the rotational axis of the holder for the finer accurate finishing cuts. Due to the lack of a rigid locking connection between the bar and holder of prior art boring head tool holders, chatter of the cutting tool caused by whipping of the bar is not uncommon, resulting in the necessity of slower cutting speeds, and inaccurate cuts due to bar slippage with the holder can occur. It is the purpose of this invention to eliminate these problems.